一种新的自动聚焦算法的研究

聚焦评价函数和极点搜索策略是自动聚焦的重要模块,直接影响聚焦的效果.为同时满足自动聚焦速度和精度上的要求,提出了一种新的自动聚焦算法.该算法综合了快速改进的灰度差分法和高精度小波变换法的优点,根据各阶段聚焦评价函数的梯度选择合适的评价函数和镜头移动步长,并且实现了从大步长快速粗扫到小步长精确细调的过渡.实验表明,与传统...     

质子交换LiNbO3波导调制器多模截止波长的测试技术研究

提出并实验了一种采用倒置输入的结构来测定Y分支LiNbO3波导相位调制器的多模截止波长的新方法,模式耦合分析表明,倒置输入的Y分支波导的多模传输的输出功率具有随波长变动发生振荡的特征,该特征可用于定量判定多模截止波长.方法的有效性得到了波束传播法(BPM)仿真和样品实验两方面的验证.     

改进型1-3压电复合材料结构参数对其谐振性能的影响

研究了水声换能器用的1-3改进型(称1-3-2型)压电复合材料的结构参数(陶瓷体积分数)对其谐振性能的影响.1-3-2型压电复合材料是由1-3型复合材料和陶瓷基底两部分组成,利用Newnham串并联理论、均匀场理论和混合定律,得到1-3-2型复合材料的压电方程,从而推导出1-3-2型复合材料的各项等效性能参数,并通过实验对频率常数、机电耦合系数和声阻抗等参数的理论推导进行了验证,实验结果与理论计算符合较好。     

反射型磁光多层膜隔离器的频率响应及宽容性研究

通过传输矩阵法分析了材料介电常数的变化对于单缺陷结构的磁光多层膜隔离器性能的响，并提出了一种多缺陷结构的磁光多层膜结构.同单缺陷结构相比，多缺陷结构的旋转角的频谱响应带宽有很大增加，对于材料介电常数变化的宽容性得到了一个数量级的提高.同时这种多缺陷的结构对于膜层厚度的变化和入射角度也有很好的宽容性. 关键词： 光隔离器 磁光效应 一维光子晶体     

Yb离子抽运动力学及脉冲储能特性研究

从准三能级Yb离子的能级结构出发，建立了Yb离子的抽运和激光速率方程，结合解析和数值方法，研究了Yb激光介质的抽运动力学过程，包括抽运激发效率、最低抽运强度、激光能量提取效率等关键参数.比较了三类典型的Yb激光介质性能：Yb:S-FAP,Yb:YAG以及Yb:FP-glass.以放大自发辐射(ASE)为设计判据，重点研究了脉冲储能型Yb激光器的设计准则，包括增益介质的厚度与掺杂浓度.最后利用此模型给出了基于Yb:S-FAP以及Yb:YAG的100J级二极管抽运固体激光器(DPSSL)的总体设计参数.将对基于Yb激光介质的脉冲储能型DPSSL的设计提供有益的参考. 关键词： Yb离子 速率方程 抽运动力学 二极管抽运固体激光器     

掺锡As2S8薄膜光折变效应及其在条波导制备中的应用研究

实验研究了Sn₁As₂₀S₇₉非晶态半导体薄膜的光折变效应及其膜厚变化的现象,归纳了沉积态样品、退火态样品和光饱和态样品的实验规律,提出和采用紫外光激励的方法试制了Sn₁As₂₀S₇₉条形波导,632.8 nm波长导模激励显示该波导具有良好的导波特性. 关键词： 光波导技术 硫属化合物玻璃 光阻断效应 光折变效应     

Characterization of iron surface modified by 2-mercaptobenzothiazole self-assembled monolayers

A self-assembled monolayer of 2-mercaptobenzothiazole (MBT) adsorbed on the iron surface was prepared. The films were characterized by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared reflection spectroscopy (FT-IR) and scanning electron microscopy (SEM). Besides, the microcalorimetry method was utilized to study the self-assembled process on iron surface and the adsorption mechanism was discussed from the power-time curve. The results indicated that MBT was able to form a film spontaneously on iron surface and the presence of it could protect iron from corrosion effectively. However, the assembling time and the concentration influence the protection efficiency. Quantum chemical calculations, according to which adsorption mechanism was discussed, could explain the experimental results to some extent.     

Tuning Pt–Cu nanostructures by bromide ions and their superior electrocatalytic activities for methanol oxidation reaction

Dendritic Pt–Cu nanoparticles were synthesized by a facile one-step method with the help of surfactant Brij58 at room temperature, and we also studied the effects of different Pt–Cu ratios on the morphology and size of nanoparticles. In addition, we further tuned the morphology of the Pt–Cu nanostructures by introducing bromide ions, eventually leading to the appearance of some tripod-like structures. Compared with dendritic Pt–Cu and commercial Pt black, these tripod-like Pt–Cu nanostructures exhibited higher electrocatalytic activity and CO tolerance for catalyzing methanol oxidation.

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First-principles study on the origin of optical transitions to be associated with F colour centers for PbWO4 crystals

The electronic structures of PbWO₄ crystals containing F type color centers with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F⁺ centers have donor energy level in forbidden band. Their optical transition energy are 1.84 eV, 2.21 eV, respectively, which corresponds to the 680 nm, 550 nm absorption bands. It predicts that the 680 nm, 550 nm absorption bands originate form the F and F⁺ centers in PbWO₄ crystals.